Citrus Industry November 201820

Editor’s note: This article grants one continuing education unit (CEU) in the Core category toward the renewal of a Florida Department of Agriculture and Consumer Services restricted-use pesticide license when the accompany-ing test is submitted and approved.

Have you recently thought about safely applying pesticides in your citrus operation? Have you won-

dered if there was a better way to do the job? Being aware of all the dif-ferent types of application methods may help you to rethink how you are doing things and allow you to increase efficiency while reducing costs. The choice of method depends on many things: target pest type and life stage, site characteristics, type of application equipment, pesticide properties and label requirements, and cost and effi-ciency of alternative methods. As the citrus industry strategizes on how best to live with HLB, perhaps it should consider different approaches to pesti-cide application.

Reviewing the different types of application methods may provide insight on how to use them differ-ently in the grove. But as a cautionary statement, as new and alternative pest control methods and techniques are tried, it is important to be sure that the label allows their use and that all label directions are followed.

BANDApplying pesticide in parallel

strips rather than uniformly over the entire field is called a band application. Band applications are used to apply pesticides, including but not limited to herbicides, in the rows or aisles. Potential herbicide drift, overspray

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Pesticide application methodsBy Juanita Popenoe

and vaporization should be taken into consideration when using this tech-nique, and the application should be done with guards or shields to min-imize contact of the herbicide to the crop plant. The growth of some citrus trees has been set back by drift from herbicides applied beneath the tree, especially with stressed trees. Special care should be taken when using her-bicides around young trees to avoid contact with the tree trunk, as injury could occur.

BASALA basal application is a low-

pressure spray directed to the lower portions of the tree trunk (from the ground up to 20 inches). This type of application is used in forestry operations with herbicides to kill undesirable trees with thin bark, and with insecticides to control bor-ers in some fruit trees. It can be a time-consuming application because each plant is treated separately and completely around the trunk, but it is very selective with nothing applied where it is not needed.

BROADCASTWhen a pesticide is applied uni-

formly to an entire area or field, it is

termed a broadcast application. An application of ant bait to an entire field would be considered broadcast because it is applied to the whole area. Broadcast applications require more pesticide than other types of applica-tions because the entire area is covered, rather than targeted plants or areas.

CRACK AND CREVICECrack and crevice application

is used in pest control in buildings. In this technique, small amounts of pesticide are placed directly into cracks and crevices of buildings, cabinets and areas where some pests commonly hide. Although not likely to be used in citrus groves, this method may be commonly used in your home, barn, packing shed or other struc-ture. The importance of having a clean, pest-free packing environment is critical to produce safety, and this technique should not be overlooked for these applications.

DIRECTED SPRAYTo minimize pesticide contact

with non-target plants and animals, a directed-spray application may be used. This is a type of spot treatment with pesticides applied directly to the pests, like a wasp nest on a building. In the future, new artificial intelligence robotic scouts may be used to iden-tify pests and be equipped to apply a directed-spray at the pests when found.

FOLIARFoliar applications are by far the

most common type of application method used in a grove. This technique directs the pesticide to the foliage of the tree and is very susceptible to drift. Foliar applications should not be used under windy conditions, although a breeze of three miles per hour can help the spray become more dispersed in the tree canopy. Drift should be minimized by not spraying into the wind, using low spray pressure and choosing nozzle tips with a larger orifice. Adjuvants may also help to reduce drift.

ROPE WICK OR WIPERA very targeted, low-volume

application is the rope-wick or wiper treatment. In this application method, the pesticide is released onto a wick that is wiped onto the target plant.

Figure 1. Basal application

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Typically it is used with herbicides to target tall weed plants emerging above the crop canopy or to selectively apply to weeds in a mixed plant commu-nity. However, this method could also be used to apply small amounts of insect pheromones or other pesticides throughout an orchard. Drift is com-pletely eliminated, but care should be taken with excessive herbicide dripping from the wick that may come into con-tact with non-target plants.

SOILApplications of pesticides directly

on or in the soil are soil applications. There are several types of soil appli-cations. Pesticides applied with this technique may be soil-active herbi-cides, systemic insecticides taken up by the roots, or pesticides targeting soil organisms. Care should be taken in this type of application to minimize leaching or runoff where excessive irrigation or rainfall could move the pesticide off target.

Relatively few pesticides are truly systemic, and it is tempting to use these exclusively because they are so easy to apply without attention to cov-erage. Because of this scarcity and the few modes of action represented, care should be taken not to overuse these chemistries and cause pest resistance to develop. Systemic soil-applied pesti-cides to control Asian citrus psyllid on young nonbearing citrus trees include only two modes of action — three neonicotinoids (all group 4A mode of action) and one group 28 insecticide. Research has indicated that repeated application of the same mode of action can lead to pesticide-resistant pest populations.

SOIL INCORPORATIONSoil incorporation is a slightly dif-

ferent type of soil application because tillage, rainfall or irrigation is used to move the pesticide into the soil. The properties of the pesticide will deter-mine which of these soil application methods is required and how much water needs to be applied to activate the pesticide but not leach it from the field or too deeply into the soil pro-file. Tillage down rows of established trees causes unacceptable levels of root damage and should be avoided with HLB-stressed trees.

SOIL INJECTIONSoil injection is the application of

a pesticide under pressure beneath the soil surface. It may be done with or without a plastic covering, depending on the pesticide properties. This tech-nique is a way to get pesticides directly to the root zone with less chance of off-target movement, but can be more time consuming than other soil applications and expensive because of specialized equipment. This technique may be used to treat soil before plant-ing row crops. Injection is the term

often used for the method of applying a pesticide injected into the irrigation system, but application through the irrigation system is technically soil incorporation, not soil injection.

SPACE TREATMENTSpace treatment is the applica-

tion of a pesticide in an enclosed area. This type of application is used on bins of fruit to control pests that might move with the fruit. California recently successfully tested a control for HLB movement between orchards

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Citrus Industry November 201822

in which harvested fruit on the truck is fogged with a carrier and a pesti-cide that destroys the disease-bearing insects before the truck leaves the orchard. The truck is driven into a specially built tarp chamber where the fogging space treatment is applied. A space treatment might also be used on containerized trees in a citrus under protective screen system that requires individual treatment because the whole tree can be treated in an enclosed space. Thermotherapy has been effective with containerized trees because the whole tree, including the root system, can be treated.

SPOT TREATMENTSpot treatment is another name

for the application of a pesticide to a small, distinct area. If scouting is done frequently enough, many pests can

be controlled with a spot treatment that limits the amount of pesticide required. However, the success of spot treatments will depend on the nature of the pest to be controlled. Some pests will require a preventive spray, rather than a limited spot treatment, to the whole field to keep them from affecting the rest of the crop.

TREE INJECTIONGetting the pesticide under the

bark of trees and into the vascular system of the plant is termed tree injection. This can be accomplished in several ways, depending on whether you are using a herbicide or another pesticide. “Hack and squirt” and “frill and girdle” are the same technique in which downward angled cuts through the bark and into the cambium are then filled with herbicide that is

gradually taken into the tree’s vascular system. “Cut stump,” in which herbi-cide is applied directly to a freshly cut stump’s cambium layer, is also consid-ered a tree injection.

In the quest for a cure for HLB, a form of tree injection is proposed to apply modified citrus tristeza virus that will produce an antibiotic protein to kill HLB in the plant, or as a way to apply antibiotics more effectively. In this type of “injection,” the pesticide is pressurized and applied to the trunk either through a gun-type applicator or through an infusion into a hole drilled in the trunk.

There are many types of pesticide application methods, although few are

usually used. Consider all the alter-native methods, including cost and efficiency. Also, take into consideration how best to achieve the desired results with your site conditions, your appli-cation equipment, and the pesticide properties and label requirements.

Juanita Popenoe is a multi-county commercial fruit Extension agent at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Lake County Extension office in Tavares.

Mail the answer sheet or a copy of the form to:

Juanita Popenoe UF/IFAS Lake County Extension 1951 Woodlea Rd. Tavares, FL 32778

If you have questions regarding this form, test or CEUs, e-mail Juanita Popenoe at jpopenoe@ufl.edu or call 352-343-4101, ext. 2727. Please allow two weeks to process your CEU request.

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Figure 3. An injection port for infusion of fungicides to combat laurel wilt in avocado

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‘Pesticide application methods’ testTo receive one Core continuing education unit (CEU), read “Pesticide application methods” in this issue of Citrus Industry magazine. Answer the 20 questions on the magazine’s website (www.CitrusIndustry.net) or mail the answers and application information to the address at the end of the article. The article and test set are valid for up to one year from the publication date. After one year, this test will no longer grant a CEU. You must answer 70 percent of the questions correctly to receive one Core CEU.

1. When making a decision about which method to use, consider (choose all that apply): a. site conditions b. target pest c. economics d. pesticide properties

2. A band application involves using a pheromone-impregnated rubber band around the tree trunk. T F

3. In a basal application, a pesticide drench is made to the roots of the plant. T F

4. Common pest control application methods used in buildings like a packing shed are the _________ and _________ applications.

5. In the future, a scout drone with artificial intelligence to identify pests may be equipped to apply which type of treatment? a. soil injection b. basal treatment c. directed spray d. space treatment

6. __________ applications are by far the most common type of application method used in a grove.

7. A wiper treatment involves: a. using a rope to wick pesticide out of a tank and into the irrigation system c. wiping insect pests off leaves b. using pesticide-wet rope to wipe over the target plant d. risky drift issues

8. Soil incorporation involves using tillage or irrigation to get the pesticide into the root zone. T F

9. Soil injection is commonly used pre-plant to inject pesticides into the soil under plastic mulch to grow row crops. T F

10. Space treatment is: a. applying pesticides on the space station c. applying pesticides into an enclosed area b. applying pesticides into an open space between the target plants d. applying pesticides to fruit before picking

11. “Hack and squirt” and “frill and girdle” are both types of tree-injection application methods. T F

12. The “cut stump” treatment involves applying a pesticide to a cut stump at least one day after the cutting. T F

13. Using a special pesticide “gun” to shoot pesticide into a tree is a form of space application. T F

14. Fire ant bait application may utilize a broadcast application method.

15. Drift can be a problem in which application method? a. tree injection b. soil injection c. foliar application d. crack and crevice application

16. Soil incorporation with tillage is a good way to get pesticide into the root zone of an HLB-stressed tree. T F

17. Drift can be minimized by not spraying into the wind and using low spray pressure and nozzle tips with a larger orifice. T F

18. A wasp nest would best be treated with which type of application method? a. broadcast application c. directed spray application b. injection application d. band application

19. Applications of pesticides directly on or in the plant are soil applications. T F

20. A basal application would be used to apply pesticides for trunk borers in a fruit tree. T F

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Pesticide Applicator CEU Form

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